REFLECTOR: Fuel Pressure == 0!?

Hiroo Umeno humeno at microsoft.com
Sun Jul 1 21:36:30 CDT 2007


I got the brakes bled and I think I got it the way I want.  It took a while to get all the bubbles to go away but I am fairly certain that they are all gone now.

On to a new problem (sigh).  While I was checking to see if the brakes will hold the plane on run-up (it did fine), I noticed that the fuel pressure was reading "0".  With the boost pump running, it was reading 3psi or so while the engine was running.

Very strange as I am used to seeing about 6-8 psi with the boost running.  The engine continued to run perfectly normally and the fuel flow was indicated at 13Gph or so when I was running at a fairly high rpm.  The fact that I get reading at all seems to indicate that the sensor is working fine.  The fact that the engine runs along happily means that there is no fuel system blockage.  I am a bit stumped.

I have a Franklin with the fuel pump AD complied with.  I also have a check valve bypass for the engine driven pump for when the fuel pump bites the dust (the fuel pump fails closed).

One thing I can think of is that if the mechanical pump actually did fail, then the carburetor is essentially "gravity fed" and it will show 0 (or very little) fuel pressure.

Does anyone know how I can check the operation of the engine driven Franklin pump?  What are the known (and likely) failure modes for these new pumps?

Hiroo
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